CA2042401A1 - Turbo blower for laser and laser oscillation device employing the turbo blower - Google Patents
Turbo blower for laser and laser oscillation device employing the turbo blowerInfo
- Publication number
- CA2042401A1 CA2042401A1 CA002042401A CA2042401A CA2042401A1 CA 2042401 A1 CA2042401 A1 CA 2042401A1 CA 002042401 A CA002042401 A CA 002042401A CA 2042401 A CA2042401 A CA 2042401A CA 2042401 A1 CA2042401 A1 CA 2042401A1
- Authority
- CA
- Canada
- Prior art keywords
- laser
- turbo blower
- bearings
- gas
- shaft
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/05—Shafts or bearings, or assemblies thereof, specially adapted for elastic fluid pumps
- F04D29/056—Bearings
- F04D29/059—Roller bearings
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/58—Cooling; Heating; Diminishing heat transfer
- F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
- F04D29/584—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps cooling or heating the machine
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/58—Cooling; Heating; Diminishing heat transfer
- F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
- F04D29/5853—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps heat insulation or conduction
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/02—Constructional details
- H01S3/03—Constructional details of gas laser discharge tubes
- H01S3/036—Means for obtaining or maintaining the desired gas pressure within the tube, e.g. by gettering, replenishing; Means for circulating the gas, e.g. for equalising the pressure within the tube
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Electromagnetism (AREA)
- Thermal Sciences (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Lasers (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
ABSTRACT
A turbo blower is used in combination with a gas laser oscillation device for machining, e.g., cutting off, workpieces. The turbo blower comprises a shaft (2) having an impeller (1) on one end thereof, a pair of bearings (5, 6) on which the shaft (2) is supported, and a motor (3, 4) for rotating the shaft. Heat radiating fins (11) are mounted on the shaft (2) for radiating the heat which is generated by a rotor (3) of the motor, thus preventing the heat Prom being transmitted to the bearings (5, 6). The heat radiating fins are forcibly cooled by a portion of a laser gas for thereby greatly increasing the heat radiation efficiency. The service life of the grease in the bearings and the bearings themselves is increased, thus reducing an expenditure of labor for grease replenishment and bearing replacement.
The bearings are also increased in reliability.
A turbo blower is used in combination with a gas laser oscillation device for machining, e.g., cutting off, workpieces. The turbo blower comprises a shaft (2) having an impeller (1) on one end thereof, a pair of bearings (5, 6) on which the shaft (2) is supported, and a motor (3, 4) for rotating the shaft. Heat radiating fins (11) are mounted on the shaft (2) for radiating the heat which is generated by a rotor (3) of the motor, thus preventing the heat Prom being transmitted to the bearings (5, 6). The heat radiating fins are forcibly cooled by a portion of a laser gas for thereby greatly increasing the heat radiation efficiency. The service life of the grease in the bearings and the bearings themselves is increased, thus reducing an expenditure of labor for grease replenishment and bearing replacement.
The bearings are also increased in reliability.
Description
-^` 20~2~01 DESCRIPTION
TURBO BLOWER FOR LASER AND LASER OSCILLATION DEVICE
EMPLOYING THE TURBO BLOWER
Technical Field The present invention relates to a laser turbo blower for forcibly circulating a laser gas in a machining gas laser device and a laser oscillation device which employs such a laser turbo blower, and more particularly to a laser turbo blower which has bearings of increased service life and is improved in reliability and maintainability, and a laser oscillation device employing such a laser turbo blower.
Baokground Art Recent carbon dioxide (CO2) gas laser osoillation devices are oapable o~ producing high output power and emitting good-quality laser beams, and are widely used in laser machining applications such as metal or nonmetal material cutting and metal material welding.
Particularly, those carbon dioxide gas laser oscillation devices which are coupled to CNC (computerized numerical control) systems to provide CNC laser machining apparatus are in widespread use in the application in which workpieces are cut to complex shapes at high speed with :, . ' '~' : .," ,...
20~2401 i hi~h preci~it)n.
One conventional carbon dioxide (CO2) gas laser oscillation device will hereinafter be described with -reference to the drawings.
FIG. 6 of the accompanying drawings shows a conventional carbon dioxide (C02 ) gas laser oscillation device in its entirety. The laser oscillation device includes a discharge tube 31 combined with an optical resonator which comprises an output coupling mirror 32 and `
a ~ully feflecting mirror 33 that are connected to respective opposite ends of the discharge tube 31. Metal electrodes 34, 35, are attached to outer peripheral surfaces of the discharge tube 31, the metal electrode 34 being grounded and the metal electrode 35 being connected IS to a high-frequency power supply 36. The high-frequency power supply 36 applies a high-~requency voltage between the metal electrodes 311, 35 to produce a glow discharge in the discharge tube 31 for laser e~citation. A laser beam is generated along an optical axis 43 in the discharge tube 31, and is emitted out of the discharge tube 31 from the output coupling mirror 32 along an optical axis 44.
8efore the gas laser oscillation device is started, the entire device is evacuated by a vacuum pump 4~, and a valve 41 is opened to introduce a laser gas at a given rate from a gas container 40 into the device until the pressure of the gas in the device reaches a 20~2401 predetermined level. The device is continuously evacuated by the vacuum pump 42 and the laser gas is continuously supplied through the valve 41 so that the laser gas is partly replaced with a fresh gas continuously while the gas pressure in the device is bent kept at the predetermined level. In this manner, the interior of the device is prevented from being contaminated by the laser gas.
In FIG. 6, a blower 39 circulates the laser gas lo in the device in order to cool the laser gas. In the carbon dioxide (C02) gas laser, about 20 ~ of the supplied electric energy is converted into a laser beam~ whereas the rest of the applied electric energy is consumed to heat the laser gas. Since the gain o~ las~r oscillation is theoretically proportional to the - t3/2)th power of the absolute temperature T, it is necessary to forcibly cool the laser gas in order to increase the oscillation e~Pioiency.
In the device shown in FIG. 6, the laser gas ~n flows through the discharge tube 31 at a rate of about 100 m/sec. in the direction indicated by the arrow into a J ~'. .
cooling unit 38~ The cooling unit 38 mainly serves to - remove the thermal energy produced by the electric ;
discharge from the laser gas. The blower 39 then ?~ compresses the laser gas which has been cooled. The compressed laser gas is thereafter introduced into the :-' ' .,:~
;' ' ' 2 ~ 0 ~
. ,~
discharge tube 31 through another cooling uni~ 37. The cooling unit 37 serves to remove the heat produced upon compression of the laser gas in the blower 39, before the laser gas is introduced again into the discharge tube 31.
The cooling units 37, 38 will not be described in detail as they are well known in the art.
The blower 39 may be either a roots blower or a turbo blower. FIG. 7 of the accompanying drawings shows the structure of a conventional turbo blower for a laser.
The turbo blower includes an impeller 1 mechanically coupled to a shaft 2 on which a rotor 3 is mounted. The rotor 3 and a stator 4 disposed therearound make up a high-frequency motor. The impeller 1 is rotated at a high speed of about 100,000 RPM by the high-frequency motor.
Because of the high rotational speed of the impeller 1, the turbo blower is smaller in volume than the roots blower which rotates at lower speeds.
The shaft 2 is supported by a pair of roller bearings 5, 6 disposed one on each side of the high-frequency motor. The roller bearings 5, 6 are lubricatedby grease in order to prevent contamination of the laser gas which would otherwise be caused by a lubricating oil mist.
The laser gas is drawn from the cooling unit 38 into the laser turbo blower as indicated by the arrow 8, and discharged from the laser turbo blower to the cooling , , .
~ 2~42~1 unit 37 as indicated by the arrow 7.
The conventional laser oscillation device shown in FIGS. 6 and 7 has suffered the following drawbacks:
Inasmuch as the conventional laser turbo blower rotates at a high speed up to 100,000 RPM, the grease tends to be deteriorated and used up eqrly. More specifically, the motor has an efficiency of about 75 %, with the rest (25 %) of the applied electric energy being converted into a heat 1QSS. Therefore, if the motor has an output of 2 kw, then about 667 W is consumed as a heat loss. About 567 W of the heat loss is caused by the iron and copper losses of the stator 4, whereas about 100 W
thereof if caused by the copper loss of the rotor 3.
When the rotor 3 is thus heated. its temperature .
goes up to 100 ~ or higher. The stator ll can be oooled by a water cooling unit disposed around the stator 4, but :
the rotor 3 cannot be cooled by a water cooling unit as it ~ :
rotates at high speed. The motor cannot be cooled by air since only the laser gas is.present under a 0.1 .: ~
~o atmospheric pressure in the motorO .~.:
Therefore, the heat generated by the rotor 3 is ~ . .
transmitted through the shaft 2 to the bearings 5, 6 fixed ~:
to the shaft 2, thus heating and increasing the temperature of the bearings 5, 6. The bearings 5 9 6 : ~ :
operate without fail up to the temperature of about 80 However, above the temperature of about 80~ , the service -` 2~2~01 I.l~@ of the hearing~ is rednced 1~2 in each incremen-t o~
10 ~ becauc;e the lubricant of the bearings is deteriorated at higher temperatures.
If the bearings were continuously operated under the above condition, the bearings would be destroyed.
Usually, therefore, the greases is replenished or the bearings are replaced at time intervals of 1000 hours. As a reslut, a large expenditure of labor has heretofore been necessary for maintenance.
1~ The grease is vaporized by the heat transmitted to the bearings 5, 6, and the grease vapor is mixed with the laser gas. The mixed grease vapor contaminates the optical components, causing laser output power reductions and mode changes.
According to the conventional structure~ the impeller 1 is positioned in the pa~sage through which a large amount o~ laser gas is circuLated. Therefore, the impeller 1 is always cooled, and temperature o~ the bearing 5 near the impeller 1 is no~ largely increased.
However, since the bearing 6 remote from the impeller 1 is not cooled by the laser gas, the bearing 6 is directly affected by the temperature rise and may be damaged highly possibly.
Disclosure of the Invention `
The present invention has been made in view of , ' ' ' .
20~2~01 ~he aforesaid drawbaaks. It is an object of the present invention to provide a laser turbo blower whose bearings are prevented from increasing their temperature and which is highly reliable and maintainable, and a laser oscillation device employing such a laser turbo blower.
To solve the above problems, there is provided in accordance with the present invention a turbo blower for a laser, comprising a shaft havinv an impeller on one end thereof, a pair of bearings on which the shaf-t is supported, and a motor for rotating the shaft, characterized in that heat radiating fins are mounted on ~ -the shaft.
There is also provided a laser oscillation device employing the turbo blower.
The heat generated by the rotor of the motor is radiated by the heat radiating ~ins on the sh~ft, and hence is prevented from being transmitted to the bearings.
The heat radiatin~ fins are forcibly cooled by a portion of a laser gas ~or ~hereby greatly inareasin~ the hea~
~n radiation efficiency. The sevice life of the grease in the bearings and the bearings themselves is increased, thus reducing an expenditure of labor for grease replenishment and bearing replacement. The bearings are also increased in reliability.
~5 Brief Description of the Drawings ..
2~2401 FI(;. I is a cross sectional view of a laser turbo blower according to a first embodiment of the present invention;
FIG. 2 is a view showing the entire structure of a laser oscillation device employing the laser turbo blower shown in FIG. 1;
FIG. 3 is a detailed view showing heat radiating fins of the laser turbo blower shown in FIG. l;
~ 'IG. Il is a cross-sectional view of a laser lo turbo blower according to a second embodiment of the present invention;
FIG. 5 is a cross-sectional view of a laser turbo blower according to a third ernbodiment of the presenk invention;
FIG. 6 is a view showing l~he entire structure oP
a conventional carbon dioxide (CO~) gas laser oscillation devioe; and FI~. 7 is a cross-seational view of a ~onventional laser turbo blower.
'~O ' .
Best Mode for Carrying Out the Invention An embodiment of the present invention will hereinafter be described with reference to the drawings.
FIG. 1 shows a laser turbo blower according to a first embodiment of the present invention. Those components shown in FIG. 1 which are identical to those 2~24~1 9 _ ~hown in FI~. 7 are denoted by identical re~erence numerals J and will no-t be described in detail. The impeller 1 is shown as being a centrifugal impeller, but may be a diagonal impeller or an axial-flow impeller.
The laser turbo blower according to the present embodiment essentially differs from the conventional laser turbo blower in that air-cooling heat radiating fins 11 are mounted on the shaft 2.
The heat radiating Pins 11 are positioned between the rotor 3 and the bearing 6 which is remote from the impeller 1. A housing 12 of the laser turbo blower has a passage for a cooling laser gas which flowes across the heat radiating fins 11 in the direction from the arrow 9 to the arr~w 10. The heat generated by the rotor 3 is removed by the heat radiating fins 11 cooled by the laser gas, and does not reach the bearing 6.
The spaces in the bearing 5, 6, other than rollers and holders between inner and outer races thereof, are ~illed with a suitable amount of ~rease.
FIG. 2 shows the entire structure of a laser oscillation device employing the laser turbo blower shown in FIG. 1. Those.parts shown in FIG. 2 which are identical to those shown in FIG. 6 are denoted by identical reference numerals, and will not be described in detail.
In this embodiment, a portion of the circulating 20~2~0~L
laser gas is supplied to a turbo blower 21 in order to cool the heat radiating fins 11 shown in FIG. 1.
Specifically, a portion of the laser gas that is cooled by the cooling unit 37 is drawn through a return passage 22 into the turbo blower 21 in the direction indicated by the arrow 9. The laser gas which has removed the heat from the heat radiating fins 11 is discharged in the direction indicated by the arrow 10, and flows back to the laser gas circulation path through a passage 23. The laser gas :~
thus returned is cooled by the cooling unit 3~ and :
circulates in the device.
Unlike the conventional turbo blower, most of the heat generated by the rotor 3 of the motor is removed by the heat radiating fins 11. ~ecause of the heat radiating fins 11, the bearing 6 is positioned as if at a greater distance from the rotor 3 which acts as a source : of heat, and is less susceptible to the heat from the .
rotor 3.
: ~ecause the heat radiating fins 11 are forcibly : ~o cooled by the laser gas, the heat generated by the rotor 3 ~ .
is transmitted through the shaft 2 and dissipated by the ;
: heat radiating fins 11.
The amount of heat q radiated by the cooling system is expressed, using a heat transfer coefficient h, as follows:
q = h- A- ~T2 - Tl) ; .;; .
20~24~1 .
-- 1, --where q is the amount o~ radiated heat (W), h the heat transfer coefficient (W/m2K), A an area through which the .
heat is transmitted (m2), and (T2 - T~) a temperature difference (K). .
The heat transfer coefficient h of the cooling system based on forced convection of a gas is expressed, using the Nusselt number Nu (dimensionless number), as .
follows:
h = Nu k/d where Nu is the Nusselt number (average), k the heat transfer coefficient (W/m2K) Gf the gas, and d the lengh :~
(diameter). `:
FIG. 3 shows in detail the heat radiating fins 11 shown in FIa. 1. It i~ assumed that the heat radiating fins have an axial lengh of 30 mm, each have a thickness tl of 2 mm, and are spaced at a distance t2 of 2 mm. The heat radiat.ing fins 11 have an outside diameter :
Dl o~ ~0 mm and an insid~ diameter D2 o~ mm, I~ the heat radiating fins 11 are used at a gas :
2n . flow rate of 0.018 (m3/s) with the gas temperature T, being 20~ and the temperature T2 of the sha~t 2 being 100~ , the amount of heat radiated by the heat radiating fins 11 is about 97 W. The heat radiating fins 11 are .
therefore sufficiently effective since the amount of heat : :
generated by the rotor 3 is about 100 W. An experiment conducted on the heat radiating fins 11 which were 20~2401 ,, actually fabricated lndicated -that they were successful in lowering the temperature of the shaft 2 from about 110 to about 50~ .
FIG. 4 shows a laser turbo blower according to a second embodiment of the present invention. Those parts shown in FIG. 4 which are identical to those shown in FIG.
1 are denoted by identical reference numerals, and will not be described in detail.
The laser turbo blower according to the second embodiment differs from the laser turbo blower shown in FIG. 1 only in that heat radiating fins 15 are also `
provided in addition to the heat radiating fins 11. The heat radiating fins 15 are positioned between the bearing 5 near the impeller 1 and the rotor 3. The housing 12 has a passage for a cooling laser gas which flows across the heat radiating fins 15 in the direo,tion ~rom the arrow 13 to the arrow 1ll. ~he heat generated by the rotor 3 is removed by the heat radiating fins 11, 15 cooled by the laser gas, and does not reach the bearing 5, 6.
FIG. 5 shows a laser turbo blower according to a third embodiment o~ the present invention. The laser turbo blower according to the third embodiment resides in that oil film dampers are disposed around the bearings 5, 6 in the laser turbo blower shown in FIG. 1~ for dampening vibrations of the bearings.
Each of the oil film dampers is composed of a ;~
_ 2~2401 sleeve 51, O-rings 52, 53, and a ~ilm of oil filled between the housing 12 and the sleeve 51.
The inner races of the roller bearings 5, 6 are fixed to the shaft 2, and the outer races thereof are -~
fixed to the sleeves 51. The housing 12 and the sleeves 51 are spaced apart from each other by gaps ranging from 10 to 100 ~ m, the gaps being filled with grease or oil.
The O-rings 52, 53 serve to isola~e the grease or oil filled in the gaps from the laser gas.
With such an arrangement, vibrations produced when the impeller 1 and the shaft 2 rotate at high speed are dampened by a fluid dynamic ef~ect of the oil film .
dampers.
While the roller bearings have been described in the above embodiments, ball bearinl3s may be employed.
The bearings may be made of oeramio.
In the above embodiments, since the bearings are prevented from increasin~ their temperature, the sevice lif`e of the bearings are increased from a conventional ?0 range of from 500 to 1000 hours to a range of from 5000 to 15000 hours. Furthermore, maintenance processes such as periodic replenishments of grease or replacement of the bearings and grease are no longer necessary. ' ~ `
As described above, inasmuch as the bearings are prevented from increasing their temperature, and maintenance processes such as periodic replenishments or ~"
- ~42~01 grease or replacement of the bearings and grease are rendered unnecessary, the laser turbo blower is improved in reliability and maintainability. .-~O ~' .' .
~0 : , . . .
~5
TURBO BLOWER FOR LASER AND LASER OSCILLATION DEVICE
EMPLOYING THE TURBO BLOWER
Technical Field The present invention relates to a laser turbo blower for forcibly circulating a laser gas in a machining gas laser device and a laser oscillation device which employs such a laser turbo blower, and more particularly to a laser turbo blower which has bearings of increased service life and is improved in reliability and maintainability, and a laser oscillation device employing such a laser turbo blower.
Baokground Art Recent carbon dioxide (CO2) gas laser osoillation devices are oapable o~ producing high output power and emitting good-quality laser beams, and are widely used in laser machining applications such as metal or nonmetal material cutting and metal material welding.
Particularly, those carbon dioxide gas laser oscillation devices which are coupled to CNC (computerized numerical control) systems to provide CNC laser machining apparatus are in widespread use in the application in which workpieces are cut to complex shapes at high speed with :, . ' '~' : .," ,...
20~2401 i hi~h preci~it)n.
One conventional carbon dioxide (CO2) gas laser oscillation device will hereinafter be described with -reference to the drawings.
FIG. 6 of the accompanying drawings shows a conventional carbon dioxide (C02 ) gas laser oscillation device in its entirety. The laser oscillation device includes a discharge tube 31 combined with an optical resonator which comprises an output coupling mirror 32 and `
a ~ully feflecting mirror 33 that are connected to respective opposite ends of the discharge tube 31. Metal electrodes 34, 35, are attached to outer peripheral surfaces of the discharge tube 31, the metal electrode 34 being grounded and the metal electrode 35 being connected IS to a high-frequency power supply 36. The high-frequency power supply 36 applies a high-~requency voltage between the metal electrodes 311, 35 to produce a glow discharge in the discharge tube 31 for laser e~citation. A laser beam is generated along an optical axis 43 in the discharge tube 31, and is emitted out of the discharge tube 31 from the output coupling mirror 32 along an optical axis 44.
8efore the gas laser oscillation device is started, the entire device is evacuated by a vacuum pump 4~, and a valve 41 is opened to introduce a laser gas at a given rate from a gas container 40 into the device until the pressure of the gas in the device reaches a 20~2401 predetermined level. The device is continuously evacuated by the vacuum pump 42 and the laser gas is continuously supplied through the valve 41 so that the laser gas is partly replaced with a fresh gas continuously while the gas pressure in the device is bent kept at the predetermined level. In this manner, the interior of the device is prevented from being contaminated by the laser gas.
In FIG. 6, a blower 39 circulates the laser gas lo in the device in order to cool the laser gas. In the carbon dioxide (C02) gas laser, about 20 ~ of the supplied electric energy is converted into a laser beam~ whereas the rest of the applied electric energy is consumed to heat the laser gas. Since the gain o~ las~r oscillation is theoretically proportional to the - t3/2)th power of the absolute temperature T, it is necessary to forcibly cool the laser gas in order to increase the oscillation e~Pioiency.
In the device shown in FIG. 6, the laser gas ~n flows through the discharge tube 31 at a rate of about 100 m/sec. in the direction indicated by the arrow into a J ~'. .
cooling unit 38~ The cooling unit 38 mainly serves to - remove the thermal energy produced by the electric ;
discharge from the laser gas. The blower 39 then ?~ compresses the laser gas which has been cooled. The compressed laser gas is thereafter introduced into the :-' ' .,:~
;' ' ' 2 ~ 0 ~
. ,~
discharge tube 31 through another cooling uni~ 37. The cooling unit 37 serves to remove the heat produced upon compression of the laser gas in the blower 39, before the laser gas is introduced again into the discharge tube 31.
The cooling units 37, 38 will not be described in detail as they are well known in the art.
The blower 39 may be either a roots blower or a turbo blower. FIG. 7 of the accompanying drawings shows the structure of a conventional turbo blower for a laser.
The turbo blower includes an impeller 1 mechanically coupled to a shaft 2 on which a rotor 3 is mounted. The rotor 3 and a stator 4 disposed therearound make up a high-frequency motor. The impeller 1 is rotated at a high speed of about 100,000 RPM by the high-frequency motor.
Because of the high rotational speed of the impeller 1, the turbo blower is smaller in volume than the roots blower which rotates at lower speeds.
The shaft 2 is supported by a pair of roller bearings 5, 6 disposed one on each side of the high-frequency motor. The roller bearings 5, 6 are lubricatedby grease in order to prevent contamination of the laser gas which would otherwise be caused by a lubricating oil mist.
The laser gas is drawn from the cooling unit 38 into the laser turbo blower as indicated by the arrow 8, and discharged from the laser turbo blower to the cooling , , .
~ 2~42~1 unit 37 as indicated by the arrow 7.
The conventional laser oscillation device shown in FIGS. 6 and 7 has suffered the following drawbacks:
Inasmuch as the conventional laser turbo blower rotates at a high speed up to 100,000 RPM, the grease tends to be deteriorated and used up eqrly. More specifically, the motor has an efficiency of about 75 %, with the rest (25 %) of the applied electric energy being converted into a heat 1QSS. Therefore, if the motor has an output of 2 kw, then about 667 W is consumed as a heat loss. About 567 W of the heat loss is caused by the iron and copper losses of the stator 4, whereas about 100 W
thereof if caused by the copper loss of the rotor 3.
When the rotor 3 is thus heated. its temperature .
goes up to 100 ~ or higher. The stator ll can be oooled by a water cooling unit disposed around the stator 4, but :
the rotor 3 cannot be cooled by a water cooling unit as it ~ :
rotates at high speed. The motor cannot be cooled by air since only the laser gas is.present under a 0.1 .: ~
~o atmospheric pressure in the motorO .~.:
Therefore, the heat generated by the rotor 3 is ~ . .
transmitted through the shaft 2 to the bearings 5, 6 fixed ~:
to the shaft 2, thus heating and increasing the temperature of the bearings 5, 6. The bearings 5 9 6 : ~ :
operate without fail up to the temperature of about 80 However, above the temperature of about 80~ , the service -` 2~2~01 I.l~@ of the hearing~ is rednced 1~2 in each incremen-t o~
10 ~ becauc;e the lubricant of the bearings is deteriorated at higher temperatures.
If the bearings were continuously operated under the above condition, the bearings would be destroyed.
Usually, therefore, the greases is replenished or the bearings are replaced at time intervals of 1000 hours. As a reslut, a large expenditure of labor has heretofore been necessary for maintenance.
1~ The grease is vaporized by the heat transmitted to the bearings 5, 6, and the grease vapor is mixed with the laser gas. The mixed grease vapor contaminates the optical components, causing laser output power reductions and mode changes.
According to the conventional structure~ the impeller 1 is positioned in the pa~sage through which a large amount o~ laser gas is circuLated. Therefore, the impeller 1 is always cooled, and temperature o~ the bearing 5 near the impeller 1 is no~ largely increased.
However, since the bearing 6 remote from the impeller 1 is not cooled by the laser gas, the bearing 6 is directly affected by the temperature rise and may be damaged highly possibly.
Disclosure of the Invention `
The present invention has been made in view of , ' ' ' .
20~2~01 ~he aforesaid drawbaaks. It is an object of the present invention to provide a laser turbo blower whose bearings are prevented from increasing their temperature and which is highly reliable and maintainable, and a laser oscillation device employing such a laser turbo blower.
To solve the above problems, there is provided in accordance with the present invention a turbo blower for a laser, comprising a shaft havinv an impeller on one end thereof, a pair of bearings on which the shaf-t is supported, and a motor for rotating the shaft, characterized in that heat radiating fins are mounted on ~ -the shaft.
There is also provided a laser oscillation device employing the turbo blower.
The heat generated by the rotor of the motor is radiated by the heat radiating ~ins on the sh~ft, and hence is prevented from being transmitted to the bearings.
The heat radiatin~ fins are forcibly cooled by a portion of a laser gas ~or ~hereby greatly inareasin~ the hea~
~n radiation efficiency. The sevice life of the grease in the bearings and the bearings themselves is increased, thus reducing an expenditure of labor for grease replenishment and bearing replacement. The bearings are also increased in reliability.
~5 Brief Description of the Drawings ..
2~2401 FI(;. I is a cross sectional view of a laser turbo blower according to a first embodiment of the present invention;
FIG. 2 is a view showing the entire structure of a laser oscillation device employing the laser turbo blower shown in FIG. 1;
FIG. 3 is a detailed view showing heat radiating fins of the laser turbo blower shown in FIG. l;
~ 'IG. Il is a cross-sectional view of a laser lo turbo blower according to a second embodiment of the present invention;
FIG. 5 is a cross-sectional view of a laser turbo blower according to a third ernbodiment of the presenk invention;
FIG. 6 is a view showing l~he entire structure oP
a conventional carbon dioxide (CO~) gas laser oscillation devioe; and FI~. 7 is a cross-seational view of a ~onventional laser turbo blower.
'~O ' .
Best Mode for Carrying Out the Invention An embodiment of the present invention will hereinafter be described with reference to the drawings.
FIG. 1 shows a laser turbo blower according to a first embodiment of the present invention. Those components shown in FIG. 1 which are identical to those 2~24~1 9 _ ~hown in FI~. 7 are denoted by identical re~erence numerals J and will no-t be described in detail. The impeller 1 is shown as being a centrifugal impeller, but may be a diagonal impeller or an axial-flow impeller.
The laser turbo blower according to the present embodiment essentially differs from the conventional laser turbo blower in that air-cooling heat radiating fins 11 are mounted on the shaft 2.
The heat radiating Pins 11 are positioned between the rotor 3 and the bearing 6 which is remote from the impeller 1. A housing 12 of the laser turbo blower has a passage for a cooling laser gas which flowes across the heat radiating fins 11 in the direction from the arrow 9 to the arr~w 10. The heat generated by the rotor 3 is removed by the heat radiating fins 11 cooled by the laser gas, and does not reach the bearing 6.
The spaces in the bearing 5, 6, other than rollers and holders between inner and outer races thereof, are ~illed with a suitable amount of ~rease.
FIG. 2 shows the entire structure of a laser oscillation device employing the laser turbo blower shown in FIG. 1. Those.parts shown in FIG. 2 which are identical to those shown in FIG. 6 are denoted by identical reference numerals, and will not be described in detail.
In this embodiment, a portion of the circulating 20~2~0~L
laser gas is supplied to a turbo blower 21 in order to cool the heat radiating fins 11 shown in FIG. 1.
Specifically, a portion of the laser gas that is cooled by the cooling unit 37 is drawn through a return passage 22 into the turbo blower 21 in the direction indicated by the arrow 9. The laser gas which has removed the heat from the heat radiating fins 11 is discharged in the direction indicated by the arrow 10, and flows back to the laser gas circulation path through a passage 23. The laser gas :~
thus returned is cooled by the cooling unit 3~ and :
circulates in the device.
Unlike the conventional turbo blower, most of the heat generated by the rotor 3 of the motor is removed by the heat radiating fins 11. ~ecause of the heat radiating fins 11, the bearing 6 is positioned as if at a greater distance from the rotor 3 which acts as a source : of heat, and is less susceptible to the heat from the .
rotor 3.
: ~ecause the heat radiating fins 11 are forcibly : ~o cooled by the laser gas, the heat generated by the rotor 3 ~ .
is transmitted through the shaft 2 and dissipated by the ;
: heat radiating fins 11.
The amount of heat q radiated by the cooling system is expressed, using a heat transfer coefficient h, as follows:
q = h- A- ~T2 - Tl) ; .;; .
20~24~1 .
-- 1, --where q is the amount o~ radiated heat (W), h the heat transfer coefficient (W/m2K), A an area through which the .
heat is transmitted (m2), and (T2 - T~) a temperature difference (K). .
The heat transfer coefficient h of the cooling system based on forced convection of a gas is expressed, using the Nusselt number Nu (dimensionless number), as .
follows:
h = Nu k/d where Nu is the Nusselt number (average), k the heat transfer coefficient (W/m2K) Gf the gas, and d the lengh :~
(diameter). `:
FIG. 3 shows in detail the heat radiating fins 11 shown in FIa. 1. It i~ assumed that the heat radiating fins have an axial lengh of 30 mm, each have a thickness tl of 2 mm, and are spaced at a distance t2 of 2 mm. The heat radiat.ing fins 11 have an outside diameter :
Dl o~ ~0 mm and an insid~ diameter D2 o~ mm, I~ the heat radiating fins 11 are used at a gas :
2n . flow rate of 0.018 (m3/s) with the gas temperature T, being 20~ and the temperature T2 of the sha~t 2 being 100~ , the amount of heat radiated by the heat radiating fins 11 is about 97 W. The heat radiating fins 11 are .
therefore sufficiently effective since the amount of heat : :
generated by the rotor 3 is about 100 W. An experiment conducted on the heat radiating fins 11 which were 20~2401 ,, actually fabricated lndicated -that they were successful in lowering the temperature of the shaft 2 from about 110 to about 50~ .
FIG. 4 shows a laser turbo blower according to a second embodiment of the present invention. Those parts shown in FIG. 4 which are identical to those shown in FIG.
1 are denoted by identical reference numerals, and will not be described in detail.
The laser turbo blower according to the second embodiment differs from the laser turbo blower shown in FIG. 1 only in that heat radiating fins 15 are also `
provided in addition to the heat radiating fins 11. The heat radiating fins 15 are positioned between the bearing 5 near the impeller 1 and the rotor 3. The housing 12 has a passage for a cooling laser gas which flows across the heat radiating fins 15 in the direo,tion ~rom the arrow 13 to the arrow 1ll. ~he heat generated by the rotor 3 is removed by the heat radiating fins 11, 15 cooled by the laser gas, and does not reach the bearing 5, 6.
FIG. 5 shows a laser turbo blower according to a third embodiment o~ the present invention. The laser turbo blower according to the third embodiment resides in that oil film dampers are disposed around the bearings 5, 6 in the laser turbo blower shown in FIG. 1~ for dampening vibrations of the bearings.
Each of the oil film dampers is composed of a ;~
_ 2~2401 sleeve 51, O-rings 52, 53, and a ~ilm of oil filled between the housing 12 and the sleeve 51.
The inner races of the roller bearings 5, 6 are fixed to the shaft 2, and the outer races thereof are -~
fixed to the sleeves 51. The housing 12 and the sleeves 51 are spaced apart from each other by gaps ranging from 10 to 100 ~ m, the gaps being filled with grease or oil.
The O-rings 52, 53 serve to isola~e the grease or oil filled in the gaps from the laser gas.
With such an arrangement, vibrations produced when the impeller 1 and the shaft 2 rotate at high speed are dampened by a fluid dynamic ef~ect of the oil film .
dampers.
While the roller bearings have been described in the above embodiments, ball bearinl3s may be employed.
The bearings may be made of oeramio.
In the above embodiments, since the bearings are prevented from increasin~ their temperature, the sevice lif`e of the bearings are increased from a conventional ?0 range of from 500 to 1000 hours to a range of from 5000 to 15000 hours. Furthermore, maintenance processes such as periodic replenishments of grease or replacement of the bearings and grease are no longer necessary. ' ~ `
As described above, inasmuch as the bearings are prevented from increasing their temperature, and maintenance processes such as periodic replenishments or ~"
- ~42~01 grease or replacement of the bearings and grease are rendered unnecessary, the laser turbo blower is improved in reliability and maintainability. .-~O ~' .' .
~0 : , . . .
~5
Claims (9)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A turbo blower for a laser, comprising a shaft having an impeller on one end thereof, a pair of bearings on which said shaft is supported, and a motor for rotating said shaft, characterized in that heat radiating fins are mounted on said shaft.
2. A turbo blower according to claim 1, wherein said heat radiating fins are cooled by a laser gas.
3. A turbo blower according to claim 1, wherein said heat radiating fins are disposed between said motor and the bearing which is positioned remotely from said impeller.
4. A turbo blower according to claim 1, wherein said heat radiating fins are disposed on both sides of said motor.
5. A turbo blower according to claim 1, 2, 3, or 4, further including oil film dampers combined with said bearings, respectively.
6. A turbo blower according to claim 1, 2, 3, 4.
or 5, wherein said bearings comprise ball bearings.
or 5, wherein said bearings comprise ball bearings.
7. A turbo blower according to claim 1, 2, 3, 4.
or 5, wherein said bearings comprise roller bearings.
or 5, wherein said bearings comprise roller bearings.
8. A turbo blower according to claim 1, 2, 3, 4.
or 5, wherein said bearings are made of ceramic.
or 5, wherein said bearings are made of ceramic.
9. A laser oscillation device comprising a discharge tube for producing an electric discharge in a gas for laser excitation, an optical resonator for causing laser oscillation, and a gas circulator having a blower and cooling units for forcibly cooling a laser gas, characterized in that said blower comprises a turbo blower according to any one of claims 1 through 9.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1259825A JPH03120882A (en) | 1989-10-04 | 1989-10-04 | Turbo blower for laser and laser oscillation device using same |
| JP259825/1989 | 1989-10-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2042401A1 true CA2042401A1 (en) | 1991-04-05 |
Family
ID=17339518
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002042401A Abandoned CA2042401A1 (en) | 1989-10-04 | 1990-09-21 | Turbo blower for laser and laser oscillation device employing the turbo blower |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5206873A (en) |
| EP (1) | EP0446369B1 (en) |
| JP (1) | JPH03120882A (en) |
| CA (1) | CA2042401A1 (en) |
| DE (1) | DE69009449T2 (en) |
| WO (1) | WO1991005384A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5317579A (en) * | 1992-08-07 | 1994-05-31 | Litton Systems, Inc. | Laser pump |
| DE4417468A1 (en) * | 1994-05-19 | 1995-11-23 | Trumpf Lasertechnik Gmbh | Gas laser appts. |
| JPH08335731A (en) * | 1995-06-06 | 1996-12-17 | Fanuc Ltd | Air blower in gas laser system |
| JP3427571B2 (en) * | 1995-06-14 | 2003-07-22 | 松下電器産業株式会社 | High-speed axial-flow gas laser oscillator |
| US6208675B1 (en) * | 1998-08-27 | 2001-03-27 | Cymer, Inc. | Blower assembly for a pulsed laser system incorporating ceramic bearings |
| US6176092B1 (en) | 1998-10-09 | 2001-01-23 | American Standard Inc. | Oil-free liquid chiller |
| JP4249723B2 (en) * | 2005-04-14 | 2009-04-08 | ファナック株式会社 | Blower for laser oscillator |
| US7535150B1 (en) | 2006-05-08 | 2009-05-19 | Prc Laser Corporation | Centrifugal turbine blower with gas foil bearings |
| JP5533318B2 (en) * | 2010-06-17 | 2014-06-25 | 株式会社Ｉｈｉ | Turbo machine |
| FR3016294B1 (en) * | 2014-01-14 | 2019-08-02 | Airfan | METHOD FOR THERMAL AND PHONIC OPTIMIZATION OF A REGULATED GAS PRODUCTION ENGINE AND CORRESPONDING RESPIRATORY ASSISTANCE APPARATUS |
| CN110735808B (en) * | 2019-11-28 | 2021-06-29 | 江苏科技大学 | Pulsating flow enhanced cooling bearing seat device |
| CN116294059B (en) * | 2023-05-12 | 2023-08-08 | 广州豪特节能环保科技股份有限公司 | Air conditioner and control method thereof |
Family Cites Families (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3638140A (en) * | 1969-07-28 | 1972-01-25 | Hughes Aircraft Co | Laser-cooling system |
| JPS4940200Y1 (en) * | 1970-06-02 | 1974-11-05 | ||
| JPS6143998Y2 (en) * | 1979-01-31 | 1986-12-11 | ||
| JPS55113391A (en) * | 1979-02-21 | 1980-09-01 | Hitachi Ltd | Gas flow type laser device |
| JPS575990U (en) * | 1980-06-10 | 1982-01-12 | ||
| JPS5814589A (en) * | 1981-07-17 | 1983-01-27 | Hitachi Ltd | Blower for laser light generating device |
| JPS59111382A (en) * | 1982-12-17 | 1984-06-27 | Hitachi Ltd | Oscillator for carbon-dioxide gas laser |
| JPS60182213U (en) * | 1984-05-15 | 1985-12-03 | カルソニックカンセイ株式会社 | Motor cooling structure for automotive air conditioners |
| DE3600126A1 (en) * | 1986-01-04 | 1987-07-16 | Fortuna Werke Maschf Ag | BLOWERS FOR CIRCUITING LARGE QUANTITIES OF GAS, IN PARTICULAR FOR HIGH-PERFORMANCE LASERS |
| JPS62137396U (en) * | 1986-02-24 | 1987-08-29 | ||
| JPS6384970U (en) * | 1986-11-25 | 1988-06-03 | ||
| DE3643735A1 (en) * | 1986-12-20 | 1988-07-07 | Tzn Forschung & Entwicklung | GAS TRANSPORT LASER |
| JPS63184381A (en) * | 1987-01-27 | 1988-07-29 | Toshiba Corp | Gas laser oscillator |
| JPH0821739B2 (en) * | 1987-06-04 | 1996-03-04 | 浜松ホトニクス株式会社 | Gas laser device |
| SE460570B (en) * | 1987-10-13 | 1989-10-23 | Trumpf Gmbh & Co | DEVICE FOR A POWER LASER |
| JP2870749B2 (en) * | 1987-10-31 | 1999-03-17 | 株式会社島津製作所 | Air conditioner for aircraft |
| JPH022695A (en) * | 1988-06-16 | 1990-01-08 | Fanuc Ltd | Laser oscillator |
| JPH025585A (en) * | 1988-06-24 | 1990-01-10 | Fanuc Ltd | Laser oscillator |
| DE68916941T2 (en) * | 1988-10-13 | 1994-12-08 | Fanuc Ltd | GAS LASER OSCILLATOR. |
-
1989
- 1989-10-04 JP JP1259825A patent/JPH03120882A/en active Pending
-
1990
- 1990-09-21 WO PCT/JP1990/001227 patent/WO1991005384A1/en active IP Right Grant
- 1990-09-21 US US07/700,174 patent/US5206873A/en not_active Expired - Fee Related
- 1990-09-21 DE DE69009449T patent/DE69009449T2/en not_active Expired - Fee Related
- 1990-09-21 EP EP90913888A patent/EP0446369B1/en not_active Expired - Lifetime
- 1990-09-21 CA CA002042401A patent/CA2042401A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| US5206873A (en) | 1993-04-27 |
| WO1991005384A1 (en) | 1991-04-18 |
| EP0446369A1 (en) | 1991-09-18 |
| DE69009449D1 (en) | 1994-07-07 |
| EP0446369A4 (en) | 1991-10-30 |
| JPH03120882A (en) | 1991-05-23 |
| DE69009449T2 (en) | 1994-09-15 |
| EP0446369B1 (en) | 1994-06-01 |
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